The present invention relates to a packet transfer method and system. More particularly, it relates to a system and method for controlling packet data transfer in mobile data communication.
Conventionally, packet transmission in a mobile communication system will be described with reference to FIG. 11. The mobile communication system includes a plurality of terminals 110a-110c, a base station 120 connected to the terminals 110a-110c via wireless lines, and a switching center 130 linked to the base station 120 via wire lines. The switching center 130 is connected to a network 140, which is one type of a public network of PSTN (Plain Service Telephone Network). Each of the terminals 11Oa-110c includes an information terminal unit and a mobile unit such as a PHS or cell phone terminal linked to the information terminal unit.
The wire line for interconnecting the base station 120 and the switching center 130 includes a shared channel and a dedicated channel. The shared channel can be shared by the multiple terminals, while the dedicated channel can exclusively be used by one of the terminals.
When a quantity of data transferred from the terminal is equal to or greater than a predetermined value, then the dedicated channel is allocated to the terminal, thereby allowing the data transferred from the terminal to be transferred through the dedicated channel.
However, in such a conventional data communication system, an enormous volume of data as well as poor quality of transmission is likely to bring about delay in data or discard of data, with concomitant reductions in processing ability and service quality in the base station and the switching center.
In view of the above problem, an object of the present invention is to provide a packet transfer method and system adapted to minimize delay in data and discard of data in the mobile communication system, and thus to provide improvements in processing ability and service quality in the base station and the switching center.
The above objective of the present invention is achieved by a data transfer method in a mobile data communication system including a mobile terminal, a base station communicated to the mobile terminal by wireless, and a switching center connected to the base station via a wire line, comprising that, when a quantity of data residing in a dedicated channel of the wire line between the base station and the switching center exceeds a predetermined. value, the dedicated channel being exclusively allocated to the mobile terminal, then a further dedicated channel is allocated to the mobile terminal, thereby transmitting the data through the multiple dedicated channels.
Further, the objective of the present invention is achieved by a data transfer method in a mobile data communication system including a mobile terminal, a base station communicated to the mobile terminal by wireless, and a switching center connected to the base station via a wire line, comprising that, when a quantity of data residing in a dedicated channel of the wire line between the base station and the switching center exceeds a predetermined value, the dedicated channel being exclusively allocated to the mobile terminal, then a shared channel to be shared by the multiple mobile terminals is applied to the mobile terminal, thereby transmitting the data through the shared channel and the dedicated channel.
A mode for carrying out the present invention will now be described. A communication system embodying the present invention includes a plurality of terminals, a base station connected to the terminals via wireless lines, and a switching center linked to the base station via a plurality of wire lines. The wire line includes a shared channel and a dedicated channel in which the shared channel can be shared by the terminals, while the dedicated channel can be used by only one of the terminals.
A packet transfer method in the communication system permits data transferred from the terminal to be transferred by packets in which the data are separated by a certain length. When a quantity of data transferred from the terminal is equal to or greater than a predetermined value, then the packet transfer method allocates the dedicated channel to the terminal, thereby permitting the data transferred from the terminal to be transferred through the dedicated channel. In the packet transfer method according to the present invention, in data transfer through the dedicated channel that is allocated to the terminal, when data transferred from the terminal is waited because of an excessive quantity of such transferred data, and further when a queuing data quantity of the data is equal to or greater than a predetermined delay data quantity-generating value, then another dedicated channel (hereinafter called an xe2x80x9cadditional dedicated channelxe2x80x9d) is allocated to the terminal, thereby transferring the data through the dedicated channel and the additional dedicated channel until the queuing data quantity is equal to or less than a predetermined delay data quantity-restoring value.
Processing to allocate the additional dedicated channel according to one embodiment of the present invention includes the following steps:
At step S1, the base station determines whether a queuing data quantity of data transferred from the terminal is equal to or greater than a delay data quantity-generating value. When the determination results in xe2x80x9cYESxe2x80x9d, then the base station requests the switching center through the shared channel to allocate the additional dedicated channel to the terminal.
At step S2, the switching center determines upon receipt of such a request from the base station whether the additional dedicated channel can be allocated to the terminal. Then, the switching center delivers the result of the determination to the base station through the shared channel.
At step S3, the base station allocates the additional dedicated channel to the terminal upon receipt of the positive result of the determination from the switching center.
Processing to release the additional dedicated channel according to one embodiment of the present invention includes the following steps:
At step S4, the base station, in which the additional dedicated channel has been allocated to the terminal, determines whether a queuing data quantity of data transferred from the terminal is equal to or less than a delay data quantity-restoring value. When the determination results in xe2x80x9cYESxe2x80x9d, then the base station requests the switching center through the shared channel to free the additional dedicated channel from the terminal.
At step S5, the switching center determines upon receipt of such a request from the base station whether the additional dedicated channel already allocated to the terminal can be released therefrom. Then, the switching center conveys the result of the determination to the base station.
At step S6, the base station releases the additional dedicated channel from the terminal upon receipt of the positive result of the determination from the switching center.
Pursuant to a preferred embodiment of the present invention, in the dedicated channel allocated to the terminal, when data transferred from the terminal is waited because of an excessive quantity of transferred data, and further when a queuing data quantity of the data is equal to or greater than a predetermined delay data quantity-generating value, then another dedicated channel (or an xe2x80x9cadditional dedicated channelxe2x80x9d) is allocated to the terminal, thereby transferring the data through the additional dedicated channel until the queuing data quantity is equal to or less than a predetermined delay data quantity-restoring value.
Processing to allocate the additional dedicated channel according to one embodiment of the present invention includes the following steps:
At step S11, the switching center determines whether a queuing data quantity of data transferred to the terminal is equal to or greater than a delay data quantity-generating value. When the determination results in xe2x80x9cYESxe2x80x9d, then the switching center requests the base station through the shared channel to allocate the additional dedicated channel to the terminal.
At step S12, the base station determines upon receipt of such a request from the switching center whether the additional dedicated channel can be allocated to the terminal. Then, the base station delivers the result of the determination to the switching center through the shared channel.
At step S13, the switching center allocates the additional dedicated channel to the terminal upon receipt of the positive result of the determination from the base station.
Processing to release the additional dedicated channel according to one embodiment of the present invention includes the following steps:
At step S14, the switching center determines whether a queuing data quantity of data transferred to the terminal is equal to or less than a delay data quantity-restoring value. When the determination results in xe2x80x9cYESxe2x80x9d, then the switching center requests the base station to release the additional dedicated channel to the terminal.
At step S15, the base station determines upon receipt of such a request from the switching center whether the additional dedicated channel already allocated to the terminal can be released from the terminal. Then, the base station conveys the result of the determination to the switching center.
At step S16, the switching center releases the additional dedicated channel from the terminal upon receipt of the positive result of the determination from the base station.
Referring now to FIG. 9, pursuant to a preferred embodiment of the present invention, the base station includes a measurement means 103, a mode-switching means 101, a control means 102, a rearrangement means 104, a multi-receiving control means 105, and a multi-receiving release means 106. The measurement means 103 permits a queuing data quantity of data transferred from the terminal to be counted for each dedicated channel, which queuing data quantity resides in a buffer. The mode-switching means 101 switches between a single channel mode and a multi-channel mode. The single channel mode permits the dedicated channel to be applied to the terminal. The multi-channel mode permits the dedicated channel and the additional dedicated channel to be applied together to said terminal. The control means 102 compares a count value obtained by the measurement means 103 with a predetermined delay data quantity-generating value, and then permits the mode-switching means 101 to switch from the single channel mode into the multi-channel mode on the base of the result of such a comparison. Meanwhile, the control means 102 compares a count value obtained by the measurement means 103 with a predetermined delay data quantity-restoring value, and then permits the mode-switching means 101 to switch from the multi-channel mode into the single channel mode on the base of the result of such a comparison. The rearrangement means 104 permits data to the terminal to be rearranged in the order of a sequence number upon receipt of the data when the mode-switching means 101 switches from the single channel mode into the multi-channel mode. The multi-receiving control means 105 requests the switching center to resend data having an expected sequence number when such data needs to be resent from the switching center to the base station because the base station does not receive the data from the switching center after a certain period of time has elapsed. The multi-receiving release means 106 confirms the absence of transferred data through the additional dedicated channel when the mode-switching means 101 switches from the multi-channel mode into the single channel mode.
Turning now to FIG. 10, pursuant to a preferred embodiment of the present invention, the switching center includes a measurement means 203, a mode-switching means 201, a control means 202, a rearrangement means 204, a multi-receiving control means 205, and a multi-receiving release means 206. The measurement means 203 permits a queuing data quantity of data transferred from the terminal to be counted for each dedicated channel, which queuing data quantity resides in a buffer. The mode-switching means 201 switches between a single channel mode and a multi-channel mode. The single channel mode permits the dedicated channel to be applied to the terminal. The multi-channel mode permits the dedicated channel and the additional dedicated channel to be applied together to the terminal. The control means 202 compares a count value obtained by the measurement means 203 with a predetermined delay data quantity-generating value, and then permits the mode-switching means 201 to switch from the single channel mode into the multi-channel mode on the base of the result of such a comparison. Meanwhile, the control means 202 compares a count value obtained by the measurement means 203 with a predetermined delay data quantity-restoring value, and then permits the mode-switching means 201 to switch from the multi-channel mode into the single channel mode on the base of the result of such a comparison. The rearrangement means 204 permits data to the terminal to be rearranged in the order of a sequence number upon receipt of the data when the mode-switching means 201 switches from the single channel mode into the multi-channel mode. The multi-receiving control means 205 requests the base station to resend data having an expected sequence number when such data needs to be resent from the base station to the switching center because the switching center does not receive the data from the base station after a certain period of time has elapsed. The multi-receiving release means 206 confirms the absence of transferred data through the additional dedicated channel when the mode-switching means 201 switches from the multi-channel mode into the single channel mode.
Pursuant to another embodiment of the present invention, in the dedicated channel exclusively allocated to the terminal, when data transferred from the terminal is waited because of an excessive quantity of transferred data, and further when a queuing data quantity of the data is equal to or greater than a delay data quantity-generating value, then a terminal ID may be provided to the transferred data in order to prevent the queuing data quantity from being equal to or greater than the delay data quantity-generating value, thereby transferring the data through the shared channel.
In this embodiment, a sending section in the base station for receiving data from the terminal and then sending the data to the switching center provides a terminal identifier to packet data that is delivered through the shared channel, not through the dedicated channel. The switching center extracts the data transmitted from the terminal through the shared channel, and then causes the extracted data to be rearranged in the order of a sequence number, together with data from the dedicated channel.
In this embodiment, a sending section in the switching center for receiving data to the terminal through a public telephone network and then sending the data to the base station provides a terminal identifier to packet data that is delivered through the shared channel, not through the dedicated channel. The base station extracts the data transmitted from the terminal through the shared channel, and then causes the extracted data to be rearranged in the order of a sequence number, together with data from the dedicated channel.